Developments have been made in the area of perpendicular magnetic recording media, with much of them focusing on increasing the recording density of the magnetic recording media by decreasing the bit error rate. A lower bit error rate can be achieved by decreasing the transition noise between adjacent bits, and the transition noise in turn can be decreased by increasing the magnetic decoupling between grains. Grains that are decoupled and magnetically isolated from one another can switch independently and may allow the media to form finer and narrower transitions.
High Ku magnetic materials are needed to keep small grains magnetic recording layer stable, but it is not easy to write to a high Ku recording layer, especially when the read/write head is small, as in high areal density magnetic recording. Media noise also increases when the Ku of the recording layer increases, and keeping magnetic core width (MCW) and magnetic write width (MWW) narrow is one of requirements for high track density.
In addition, signal-to-noise ratio (SNR), overwrite (OW), and MCW are a trilemma when designing high areal density perpendicular recording media. There is a trade-off among the three parameters. However, high performance perpendicular magnetic recording media requires continuous improvement on all the three key parameters. Several researchers have reported that exchange coupled composite media comprising hard and soft layers improve both SNR and OW. (Jian-Ping Wang et al., IEEE Trans. Mag., 2005, Y. Inaba et al., IEEE Trans. Mag., 2005). Proposed materials for the exchange coupling layer have been CoRu or CoCrPtB (Gunn Choe et al., IEEE Trans. Mag., 2009). What is needed are new materials for the exchange coupling layer which improves OW, MCW, and SNR.
Therefore, it would be beneficial to the improvement of perpendicular recording media to magnetically decouple the magnetic grains of the magnetic layer of a magnetic recording medium.